Prior art rectangular balers are used to gather crop material that has been deposited on the ground in swaths or windrows and to pack the crop into tied bales. Such balers are typically towed by a tractor and driven by the power take off (PTO) shaft of the tractor.
Rectangular balers have a baling chamber with a reciprocating plunger at one end and a bale outlet at the other end. An intake duct communicates with the baling chamber near the end which is closed by the passing plunger. Crop material is loaded into the intake duct by a pickup to form a slice of crop material. Once the slice has reached a desired density, a so-called stuffer transfers the slice into the baling chamber where it is compressed by the plunger against the crop material already present in the baling chamber. After a bale of the desired size has been formed by compressing several such slices, twine is wrapped around the bale and tied. The tied bale moves through the bale chamber to the outlet whilst offering resistance to allow the next bale to be compressed.
The present invention is concerned with the preparation of slices within the intake duct and with the transfer of the slices by the stuffer from the intake duct into the baling chamber.
The intake duct communicates at its upper end with the baling chamber and at its lower end with a packer or rotor. The packer or rotor has rotating blades or tines that propel the crop material picked up from the ground towards the upper end of the duct. Once the crop material attains a desired density within the intake duct, which may be determined e.g. by a sensor, a cycle of the stuffer is commenced to transfer that slice into the baling chamber.
In certain prior art balers the stuffer operates in the same manner as a rake and has two mechanically driven arms carrying a tine bar at their free end. The upper wall of the intake duct has elongated slots that allow the tines of the stuffer to enter into the duct to engage the crop material packed within it. The movement of the arms causes the tines to follow a generally kidney shaped path so that they sweep along the entire intake duct to push the slice into the baling chamber. On reaching the upper end of the intake duct, they are retracted from the intake duct and return outside the intake duct to a position near the lower end of the duct in readiness for the next stuffer cycle. A problem that can be encountered is that the packer cannot propel the crop material sufficiently into the intake duct to achieve an even distribution within the intake duct. As a result, the crop material is denser near the packer than at its upper end near the baling chamber. Aside from creating bales of uneven density, there is a risk that clogging may occur near the lower end of the intake duct.
To address this problem U.S. Pat. No. 6,050,074 teaches using the stuffer to assist in redistributing the crop material within the intake duct. This is achieved by operating the stuffer in one of two modes. In a first mode, the stuffer performs a short packer stroke so that it only displaces the crop material partially along the intake duct. In the second mode, the stuffer performs a full stuffer stroke to transfer the contents of the intake duct into the baling chamber. The mechanism of U.S. Pat. No. 6,050,074 has the disadvantage of using a complex system of levers.
EP 2 713 704 also operates in two modes but uses a simpler and more compact stuffer drive mechanism. The stuffer of EP 2 713 704 comprises a stuffer arm connected at a first pivot point to a crank arm that is driven to rotate at a multiple of the cycling rate of the plunger, and the stuffer arm is acted upon at a second pivot point by a cam track and follower arrangement selectively driveable in synchronism with the crank arm by way of a disengageable clutch. In one mode, the second pivot point of the stuffer arm is held stationary, wherein the tines disposed on its free end follow a first kidney shaped path. The maximum depth of the path is determined by the length of the crank arm but the length of its sweep through the intake duct will depend on the position of the second pivot point relative to the axis of rotation of the crank arm and relative to the intake duct.